Halogen, Heat, Hype and Hysteria

by Eric Strandberg LC,

Lighting Design Lab

As halogen light bulbs (lamps) gain more market share and find their way into more residential applications the controversy around them continues. Some marketers make questionable claims about their products. (The Lab has a 300W torchiere on display that is boldly labeled "Environmentally Responsible Lighting"…which, by the way, couldn't be farther from the truth). Safety and consumer groups urge caution about the hazards of halogen sources for reasons ranging from excess heat to ultra-violet emissions.

This article attempts to put some of these issues into perspective and to dispel some myths.

Myth #1: Halogen is much brighter. True and False. In the case of directional sources such as PAR lamps and MR16s (low voltage), the halogens have a much higher center beam candlepower (CBCP), largely due to more precise beam control, than non-halogen PAR or R type lamps. Lets look at some 30 degree "flood" lamps (note the longer lamp life too).
65 watt PAR standard- 1700 CBCP, 1750 hours
60 watt PAR halogen- 2500 CBCP, 3000 hours
50 watt MR16 low voltage halogen- 2500 CBCP, 6000 hours

However in the case of 'A' style lamps (standard omni-directional lamps) the brightness difference is just about a wash, with the halogen lamp providing only about 10% more lumens. But the halogen does have about twice the lamp life.

100 watt standard- 1700 lumens, 1000 hours.
100 watt halogen- 1850 lumens, 2250 hours (see note 1 below).
When comparing higher wattage lamps, the standard incandescent is actually brighter.
300W "A" standard- 6200 lumens, 750 hours
300W T-3 halogen- 5950 lumens, 2000 hours.(commonly used in torchieres)
For fixture designers the big advantage with halogen is small size. The 'A' lamp is about the size of an lemon and almost 7" long while the T-3 halogen is about as big as a string bean. This brings us to myth #2.

Myth #2: Halogen is hotter. True and false. A 300W incandescent lamp gives off the same amount of heat regardless of its size, shape or type. However because most halogen lamps are small they have very little surface area and their bulb wall temperatures can be extremely high. This can lead to the fires in which halogen torchieres are so notorious. Many of the modern low voltage desk lamps have a 50W halogen bulb smaller than a peanut. Compare it to an "A" lamp (the size of a lemon) and its not hard to imagine which would give you a burn faster due to less surface area. However, if properly used and shielded, the small halogen lamps can make for interesting and safe fixture designs. Another way in which halogen can be perceived as hotter is through light concentration. As stated earlier, the halogen PAR lamps have more precise beam control resulting in more light and heat being directed in the beam angle. This brings us to myth # 3.

Myth #3: Halogen is more efficient. True and false...mostly true. For the most part the halogen products deliver more lumens per watt than conventional tungsten lamps. But it is up to the user to apply the appropriate wattage to achieve the proper light levels. A 75W halogen PAR30 uses just as much energy as the 75W R30 it replaces. (It will be brighter, which may or may not be a good thing.) I cringe when I see one of those square halogen floods being used to light a small parking area. These fixtures are usually at least 300W and unless you are planning to do surgery in the parking lot it is far more light than needed for most tasks. Probably the most efficient of the halogens is the low voltage MR16 (but not for parking lots).
Lets compare some common 50W lamps with similar beam spreads:
50ER30 = 1200 CBCP, 2000 hrs
50PAR30/H = 2000 CBCP, 2000 hrs
50PAR30HIR 2 = 3000 CBCP, 3000 hrs (see note 2 below)
50MR16 = 3160 CBCP, 5000 hrs!
Remember, these all use the same amount of power! The savvy designer may use a lower wattage lamp or use a wider beam spread and less fixtures.

Myth #4: Halogen is an ultraviolet radiation (UV) hazard. False and true, mostly false. A standard incandescent lamp emits about 75 micro watts per lumen(µW/lm) of UV, and unshielded halogen emits 100- 200 µW/lm. (Compare this to daylight, which emits 300 - 600 µW/lm!) However Underwriters Laboratories now requires halogen lamps and/or fixtures to incorporate a glass shield that brings the UV emissions down to a negligible level. For example, an MR16 with a cover glass takes over 30 times as long to emit the same amount of UV as an MR16 without a cover glass.

Source: http://www.elflist.com
Image: www.lightbulbs2u.com